Nerves of the Thoracic Wall

The thoracic wall is supplied by the intercostal nerves which are the anterior primary rami of spinal nerves. A typical spinal nerve is shown in the adjacent diagram.

spinal cord (1)

dorsal (sensory, afferent) root (3)

ventral (motor, efferent) root (2)

spinal nerve (4)

dorsal primary ramus (mixed) (5)

ventral primary ramus (mixed) (6)

white communicating ramus (8)

gray communicating ramus (7)

sympathetic ganglion (9)

Once you have the names down, you should try to understand what is going on in each of the branches.

Starting at the spinal cord, we can work our way out to the periphery describing how a spinal nerve is formed and how it branches.

When the spinal cord is examined in cross section you can usually pick out two colors on its surface: white and gray. This is called the white matter and the gray matter of the spinal cord. The gray matter forms a butterfly-like image with dorsal horns and ventral horns.

The white matter is made up mostly of nerve fibers running up and down the spinal cord. The gray matter is made up mainly of cell bodies of nerve cells, this giving a grayer appearance.